I have just received my Pi 4 and with it an alloy heatsink case with fans and the 3.5" LCD Touch screen.
You can imagine my dismay when I discover that these two accessories do not play well together as they both require the 5v and GND pins for operation.
What effective solution is there for this conundrum.
I think you will need to supply more details.
There are multiple ground pins and 2 5 volt pins
The 3.5” touchscreen totally covers any 5v GPIO pins with its header connector. This means there is no 5 volts pin available for the fan power.
It looks to me that the header that would plug into the GPIO pins is not long enough to get over the allow heatsink case with fans. I think that it would need an extended header plug.